1. Field of the Invention
Embodiments of the invention generally pertain to the field of materials processing and associates processed materials. More particularly, embodiments of the invention are directed to methods for processing materials using femtosecond duration laser pulses, applications of such methods, and materials and/or material properties resulting from such methods. Even more particularly, embodiments of the invention are directed to methods for altering the surface structure of metal materials using femtosecond duration laser pulses, applications of such methods, and materials and/or material properties resulting from such methods, including blackened and colored metals.
2. Description of Related Art
Although materials may be shaped or otherwise altered in a large variety of ways including milling, machining, grinding, etc., in recent years, laser-based alteration of materials has become a common method for a variety of materials processing applications. For example, laser alteration of materials by high energy laser pulses has been used to both create precise hole patterns in metals or metal films as well as for more subtle material alterations such as texturing of metals or metal films by the intense heating/melting/vaporization effects of such high energy laser beams.
Reported methods of laser alteration of materials involve the use of ‘short-duration’ (i.e., nanosecond (ns) and picosecond (ps)) laser pulses. See, for example, U.S. Pat. Nos. 5,635,089 and 4,972,061. U.S. Pat. No. 6,979,798 describes the use of laser pulses of preferably less than 130 femtoseconds (fs) to specifically burn metal links on integrated circuits. Thus the use of ultrashort (ns) duration laser pulses for laser processing of materials may achieve results that are different than those from longer duration (i.e., ‘short’) laser pulses. The duration of a nanosecond laser pulse is long enough for the pulse to interact with the material as it is ejected from the surface. Ultra-short duration, femtosecond (fs) laser pulses, by comparison, are not long enough in duration to interact with the material ejected from the surface of the irradiated substance, since the pulse ends long before the hydrodynamic expansion of the ejected material. Another difference between different laser pulse timescales is that the laser-supported combustion and detonation waves that are commonly generated in a nanosecond duration laser pulse do not occur in an ultra-short fs laser pulse, again offering up the possibility of materials processing effects and resulting material parameters that may be difficult or impossible to obtain with longer duration laser irradiation.
In light of the above observations, advantageous benefits may be obtained from the use of ultra-short, femtosecond pulses in the processing of certain materials and the altered materials or material characteristics resulting from processing with one or more fs laser pulses. Certain advantageous benefits may also be realized by the ability to controllably modify optical properties of a metal.